Zhibiao Hu

LaF3-coated Li[Li0.2Mn0.56Ni0.16Co0.08]O2 as cathode material with improved electrochemical performance for lithium ion batteries

In this article, the pristine Li-rich layered oxide Li[Li0.2Mn0.56Ni0.16Co0.08]O2 porous microspheres have been successfully synthesized using a urea combustion method and then coated with 1 wt% LaF3 via a facile chemical precipitation route. The structures and morphologies of both pristine and LaF3 coated Li1.2Mn0.54Ni0.16Co0.08O2 were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HR-TEM). The results reveal that the obtained particles possesses the morphology of porous microspheres and a LaF3 layer with a thickness of 5–8 nm coated on the surface of the Li[Li0.2Mn0.56Ni0.16Co0.08]O2 particles. As lithium ion battery cathodes, the LaF3 coated sample, compared with the pristine one, has shown a significantly improved electrochemical performance; the initial coulombic efficiency improves from 75.36% to 80.01% and the rate compatibility increased from 57.4 mA h g−1 to an extremely high capacity of 153.5 mA h g−1 at 5 C. Decreased electrochemical impedance spectroscopy (EIS) reveals that the enhanced electrochemical performance of the surface coating was attributed to the lower charge transfer resistance of the sample.

Facile synthesis of selenium/potassium tartrate derived porous carbon composite as an advanced Li–Se battery cathode

Porous carbon with a unique 3D structure has been prepared by the immediate carbonization of potassium tartrate. At an optimal carbonization temperature of 700 °C, the carbon mainly composed of micro- and small meso-porous structure has a Brunauer–Emmett–Teller (BET) specific surface area of 816.2 m2 g−1, and the element Se with an amorphous structure is uniformly encapsulated into the porous structure of carbon. The weight ratio of Se in the composite can reach ∼50%. As the Li–Se battery cathode, the composite shows a (2nd) reversible discharge capacity of 550.5 mA h g−1 with an initial coulombic efficiency of 68.2% at 0.24C, and a discharge capacity of 485.3 mA h g−1 can be retained after 80 cycles. Even at a high current density of 1.2C, the cell also delivers a stable discharge capacity of about 452.3 mA h g−1. The good electrochemical performances of the as-prepared composite may be attributed to high specific surface area and small porous size.